Risk versus Reward
HPKP mitigates a very specific scenario: someone persuades a CA to issue a certificate for your website to them, AND they successfully implement a DNS poisoning attack to redirect traffic to their fake version of their site AND user has visited your site so has the HPKP policy cached. In that case HPKP will prevent a user visiting the fake site over HTTPS.
I don't think that's a common scenario except for some very high profile targets.
Additionally HPKP is deliberately not used for locally installed certs (or they would break local proxies and anti-virus scanners that create dummy certs automatically). A massive hole in this feature. To me a bad locally installed cert (e.g. Superfish) is much more likely than above scenario and this does nothing to protect against that.
The risk to DOSing your own your site are HUGE. Just changing a cert will break your site unless you remember to update your HPKP policy in advance by the Time to Live amount. Yes you can pin the key (and get a new cert for same key - itself a bad practice), or use backup keys/certs, or pin either an intermediate cert or root cert but requires a lot of thought. And a lot of assumptions about which path will be used to go from your leaf cert to a trusted root cert. That's not to mention added complexity when the next SHA-2 style upgrade comes along, or you want to change cert provider and your path changes.
Personally I wouldn't recommend it. I just don't see the reward compared to the low risk it mitigates and high risk it introduces.